Dribbble (yes, there are three b's) is an invite-only design gallery that takes a Twitter approach to showcasing work. Rather than limit by characters, 120,000 pixels are allowed in each post. The idea here is for designers, web developers, illustrators, and others to share their work-in-progress, only revealing a small portion of it before it's public.
The design of the Dribbble website is clean and modern, and they have managed to keep the quality of work on the site quite high. Each "shot" (a single screenshot image) is 400 × 300 pixels or less and accompanied by view tracking, "likes," tags, comments and an easy way to tweet the shot or link to it with a pre-built short URL. Members are given up to 24 shots per month. The interface makes it easy to interact with the community... assuming you're part of it, that is. What results is a site with an exclusive feel, tons of inspiration, and a buzz around it, mostly from people wanting invites.
Some recent shots that caught my attention:
There is no sign-up form on Dribbble. While the website is invite-only, all new members are invited by existing "players," allowing the community to grow while keeping the quality of work high. Members are given a certain number of invites (and "routinely" given new ones), so the responsibility of maintaining that quality squarely rests on the shoulder's of the users. Lately, people have been custom-designing pages just to ask, and in some cases, beg, to become a Dribbble player.